Oil Extraction from Castor Cake Using Ethanol: Kinetics and Thermodynamics

In this study, the kinetics and thermodynamics of oil extraction from castor cake using ethanol were investigated. Castor cake had a total oil content of 14.78 ± 0.12% in mass and the average particle diameter was 0.446 mm. Oil extractions were carried out in a stirred batch extractor system at various temperatures (20, 30, 40, and 55 °C). The fit of three different kinetic models to the experimental data was tested, with a modified Fick’s Law model being the most appropriate to describe the extraction kinetics ( r 2 ≥ 0.960 and ARE ≤ 3.25%). Effective diffusion coefficients were determined, ranging from 4.52 × 10 –13 m 2 s –1 at 20 °C to 5.60 × 10 –13 m 2 s –1 at 55 °C. Change in Gibbs’ free energy (Δ G °) was determined to be negative (−4.55 kJ mol –1 at 20 °C to −6.56 kJ mol –1 at 55 °C), while changes in enthalpy (Δ H °) and entropy (Δ S °) were positive (12.27 kJ mol –1 and 57.41 J mol –1 K –1, respectively).